March 30, 2015

Homework Help: physics (thxs again)

Posted by susan on Wednesday, March 14, 2007 at 7:48pm.

Thank you for the help :)

A certain sample carries a current of 4A when the potential difference is 2V and a current of 10A when the potential difference is 4V. This samples is:
a) obeys ohm's law
b) has a resistance of 0.5 ohms at 1V
c) has a resistance of 2.5 ohms at 1V
d) has a resistance of 2.5ohms at 2V
e) does not have a resistance

I treated each pathway separately so I have
R= V/I = (2/4)= .5
R= V/I= (4/10) = .4
The answer says that it is B. I am not quiet seeing how they get that answer.

An certain resistor dissipates electrical energy at a rate of 0.5 W when connected to a 3V potential difference. When connected to a 1V potential difference, the rate of electrical dissipation:
a).5 W
B) .167 W
C) 1.5W
D) .056W
E) none of these

I am little unsure about how to go about this problem. The main equation I got was P= V^2/R. The question seems to only want power.

Pm the first, there is no correct answer.

On the second, Power= v^2/resistance so as voltage decreases by 1/3, power decreases by 1/9. One-ninth of .5 watts is ...

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